There are therefore provisional, and, if one may so speak, temporary truths. Does science ever establish any others? The ideas which Hipparchus and the Greek astronomers had of the heavens was not false in all respects. It was the astronomical truth compatible with the conditions of the society in which they lived. After the labours of the observers of the Middle Ages, utilised by Copernicus, this idea faded before another one which became more perfect with Newton and Laplace. Perhaps this one will be modified in its turn, in consequence of new discoveries! Similarly it was thought that the earth was a flat surface, then a round disc. Then it was represented as a sphere and finally as an ellipsoid. To-day we know that this ellipsoid is irregular. Truth is then at each period “the perfect logical coherence,” or the correspondence between our conceptions and our observations. The history of human thought is composed of a progressive series of alternating periods. At a certain moment the mind has placed what it conceives in accordance with what it knows. But, by degrees, new facts are observed, known facts are better interpreted, discoveries burst forth. The harmony between the conceptions and the observations then becomes precarious. Minds find a greater and greater difficulty in fitting all the acquired knowledge into the traditional frame. At last the frame gives way. Then the harmony is re-established in a more comprehensive form, which in its turn is destined to become insufficient. Here positive philosophy recognises a sociological law. It gives up the vain dream of immutable truth. It no longer regards the truth of to-day as absolutely true, nor the truth of yesterday as absolutely false. It ceases to be critical in regard to the past.” To conclude, the theory of science can therefore only be accomplished from the sociological point of view. It remains imperfect so long as “we” has not been substituted to “I,” the universal subject which is humanity to the individual subject, and a philosophical history of the sciences to mere reflective analysis. To the logical conditions of science, to define it completely, its biological and social conditions must be joined. Then, but then only, it will be understood, that, at each period, science is at the same time true and relative, without its relativity placing its truth in danger. FOOTNOTES: [31] 1 Cours, vi. 651-3. [32] 2 Cours, vi. 651-3. [33] Discours sur l’esprit positif, p. 16; Pol. pos. III, 25. [34] Cours, III, 4. [35] Cours, VI, 647. [36] Cours, I. 108: II. 18, 188-9. [37] Cours, VI. 646 sqq. [38] Cours, II. 18: III, 11-12. [39] Cours, IV, 147. [40] Cours, II, 195-7. [41] Cours, II, 187. [42] Cours, IV, 672-3. [43] Revue générale des Sciences, 30 septembre, 1897. [44] Discours sur l’Esprit positif, p. 15. [45] Cours, 756., VI. CHAPTER V SCIENCE (CONTINUED) PHENOMENA AND LAWS